Diagnosing disorders and afflictions in the human brain with non-invasive procedures is important medically and scientifically.
This invention relates to determining the nature of brain lesions using quantitative electrophysiology. In particular, the invention relates to analyzing electroencephalographic information in a manner to permit assessment of the nature of brain lesions. The invention is further directed to give a characterization of afflictions such as dementia, being selective for multi-infarct dementia or Alzheimer's disease, Pick's disease and demyelinating diseases such as multiple sclerosis.
Brain imaging used by physicians in clinical practice includes structural imaging and functional imaging. Structural imaging is effected by computed axial tomography (CAT) scanning or magnetic resonance imaging (MRI) scanning. Functional imaging is effected by positron emission tomography (PET), single photon emission computed tomography (SPECT) or electroencephalography (EEG).
Structural imaging is performed for determining the location of a brain tumor or other kind of gross structural alteration of the brain. Functional imaging tests are performed to determine functional alteration in the brain where there may not be significant structural alteration. These broad categories of tests are complementary. A physician evaluating a neurological or psychiatric illness could perform a test from both categories to assess and/or diagnose a patient's condition. The present invention particularly concerns functional imaging.
PET scanning measures brain metabolism and can identify areas that are hypoactive. SPECT scanning measures cerebral blood flow, which is an indirect measure of metabolism and therefore brain function. Both of these technologies yield useful physiological information. For example, Alzheimer's disease presents with hypometabolism or hypoperfusion of the parietal lobes bilaterally and multi-infarct dementia presents with multiple foci of hypometabolism and hypoperfusion. PET and SPECT scanning are expensive, requiring investments of millions of dollars initially. Also required are many hours of technician time per test and the production and injection of radionuclides into a patient.
EEG brain mapping is relatively less expensive and can be performed without the need for radionuclides. Technician time for performing the scan also is less costly. A disadvantage of EEG mapping, however, is that it has not been possible to analyze the information obtained by the electroencephalogram to diagnose and assess effectively different conditions of the brain, and thus diseases and disorders of the brain.
Information which is obtainable from an EEG includes conventional EEG data representative of electrical activity in different brain regions. When this data is digitized and processed as in quantitative EEG ("qEEG"), it is possible to obtain topographical brain mapping of electrical activity in different brain regions. From a qEEG unit, it is also possible to obtain measurements of absolute power and relative power, and evoked potentials. Quantitative EEG techniques represent an advance over traditional EEG methods because they permit the detection of trends which are difficult or impossible to discern by direct visual inspection of the EEG voltage tracings. Previous efforts to generate images depicting quantitative EEG data have had limited clinical applicability because they have not been shown convincingly to be associated with specific clinical syndromes or diagnoses; for example, the presence of a qEEG brain map of regions with large amounts of power in the delta band may reflect an electrophysiologic encephalopathy from many diseases, without distinguishing between them.
A shortfall of all these EEG and qEEG data and information which are analyzed independently is the inability to provide information regarding brain physiology that is substantially equivalent to information from PET or SPECT scans.